Hydrophobe-modified, water-soluble polymers, e.g., hydrophobically modified cellulose ethers, have found extensive use in the latex paint industry as additives to provide associative thickening and rheology modification. Associative thickening can be described as a thickening mechanism whereby the hydrophobic substituents of the polymer molecules interact with each other to provide desirable thickening characteristics such as high viscosity at low shear. In many cases, the hydrophobic substituents of the polymers can affect the rheology of the latex composition providing enhanced flow and leveling properties. Typical hydrophobic substituents used to derivatize polymers such as cellulose ethers include long chain alkyl epoxides, e.g., 1,2-epoxyhexadecane and glycidyl ethers with long alkyl chains, e.g., nonylphenyl glycidyl ether. Thus, the hydrophobe-modified, water- soluble polymers are desirable additives in latex compositions.
In contrast to latex compositions, oil-based compositions, e.g., oil-based paints, commonly employ vegetable oils such as linseed oil or tung oil as a component of the vehicle in the paint. These vegetable oils, which are also referred to in the art as "drying oils", form crosslinked films upon exposure to air. Like all vegetable oils, these drying oils are triesters of various fatty acids and glycerol. However, unlike most vegetable oils, the fatty acids in drying oils typically comprise three unsaturated fatty acids: oleic (9-cis-octadecenoic); linoleic (9-cis-12-cis-octadecenoic) and linolenic (9-cis-12-cis-15-cis-octadecenoic) acids. The use of such crosslinkable drying oils in oil based paints helps to provide a paint film which is hard and durable. Thus, the drying oils are desirable components of oil-based compositions. However, oil based compositions typically comprise large proportions of volatile organic compounds ("VOC's") e.g., 380 to 450 grams per liter ("g/l") or more. Such high concentrations of VOC's are environmentally undesirable.
Latex compositions, on the other hand, typically comprise very low concentrations of VOC's, e.g. less than about 250 g/l and thus are more environmentally compatible. Accordingly, it would be desirable to incorporate the drying oils of oil-based compositions into latex compositions to promote crosslinking of the latex compositions. However, the drying oils used in oil-based compositions are not water-soluble and accordingly cannot readily be used in latex compositions. Also, the unsaturated fatty acids which comprise the drying oils are not readily convertible to a chemical form which can be reacted with cellulose ether to provide hydrophobe modification.
Accordingly, hydrophobe-modified cellulose ether derivatives are desired which can provide associative thickening and rheological modification properties to latex compositions for the purposes of storage and application of the latex to a surface to be coated, and which can also promote crosslinking of the latex composition upon exposure to oxygen after the composition has been applied to the surface to be coated.